The present invention relates to a continuous boring or cutting machine provided with tools animated by a sweeping movement.
These machines, which are particularly used for driving tunnels, are known for example by French Patent 1 597 434 and its Additions.
The third Addition 71 17770 to this Patent describes a machine comprising a plurality of tool holders mounted to oscillate on a common rotating structure, these oscillations being controlled in synchronism by a rotary jack coaxial with respect to the rotating structure, the rod of said jack being fast with an element to which each tool-holder is connected by an individual mechanical transmission essentially comprising an eccentric.
FIG. 1 of the accompanying drawings, which is taken from Addition 71 17770, schematically illustrates such a machine.
In This Figure, which is a view in longitudinal projection, the tool-holders 1, on which the tool or tools disposed at their ends have not been shown, are driven by a central piston rod 2 reciprocable along an axis on bearings 2a inside the hollow shaft 3 of the movable head 4 rotating between bearings 5. This rod 2 is fast with the piston 6 of a double acting jack 7, the cylinder 8 of which is supplied with pressurised oil via fixed tubes 9 through the rotating seal 10.
The tool-holder 1 is mounted on the shaft 12 which extends perpendicular to the axis for piston rod 2 and is fixed on an element 11 carried by the rotating head 4, and the connection of the tool-holder with the rod 2 is effected by a ball-and-socket joint 13 with eccentric axis 14 carried by an element 15 fixed to the end of the rod 2 opposite jack 7.
In practice, it is noted that a transmission thus produced by an eccentric may, in certain cases, and particularly when the machine is designed to drive tunnels of small diameter, of the order of 3 meters, give rise to risks of blocking due to the eccentrics.